The invention relates to improvements in apparatus for acting upon (particularly for reducing or eliminating) occlusions and stenoses in veins and other body cavities, such as intravascular blockages.
Certain heretofore known apparatus for the treatment of stenoses employ balloons which are inflated subsequent to introduction of a balloon carrier, such as a catheter, into the body cavity. The balloon constitutes or is affixed to the distal end of the catheter and is inflated when the distal end of the catheter reaches an occlusion or a stenosis. A drawback of such apparatus (reference may be had, for example, to German Utility Model No. G 88 05 709.7 of Angiomedics, published Sep. 15, 1988) is that the balloon cannot be introduced into a very narrow constriction and cannot penetrate into an occlusion in a relatively narrow blood vessel or another body cavity.
It was also proposed to employ a rotary catheter, particularly for reopening of occluded blood vessels. An advantage of apparatus which employ a rotary catheter is that the distal end of the rotary catheter can be more readily introduced into a body cavity than a catheter which is merely pushed into the cavity but does not rotate about its longitudinal axis. The reason is that the friction between the distal end of a rotary catheter and the wall surrounding a body cavity which is to receive the catheter is much less pronounced than when a nonrotating catheter is forced into a body cavity. The rotary catheter has an olive-shaped or a similar substantially ellipsoidal distal end which is caused to penetrate into an obstruction in a body cavity and to enlarge the passage as the rotating catheter continues to advance. Such enlargement involves displacement and compression of material which surrounds an obstruction. The substantially ellipsoidal distal end of the rotating catheter seeks the path of least resistance and thus advances, or is expected to advance, into and through the still unsealed portion of the passage within a stenosis or into that (normally central) part of an occlusion which was last to develop.
It is also known to confine a rotary catheter in a second or protective catheter which does not or need not rotate. The purpose of the second catheter is to prevent undue flexing of the normally highly flexible rotary catheter. Such prevention of undue flexing is desirable and advantageous because, when properly guided, the rotary catheter is more likely to rapidly advance toward the situs of an occlusion or stenosis. However, the non-rotating second catheter also exhibits certain serious drawbacks. Thus, the two catheters define an annular clearance which is rapidly filled with blood or with another body fluid, and such fluid opposes (and can prevent) rotation of the inner catheter.
Another drawback of conventional apparatus which employ rotary catheters is that the rotary catheter must be highly flexible in order to avoid puncturing of and/or other damage to the wall surrounding a blood vessel or another body cavity. On the other hand, if the apparatus is to treat an occlusion which contains a very hard substance (such as plaque), the occlusion cannot be successfully attacked by resorting to a highly flexible rotary catheter. In fact, the rotary catheter is often incapable of successfully acting upon an occlusion or a stenosis even if it is stiffened by a second or outer catheter which is not rotated during introduction into a blood vessel or into another body cavity.
European patent application No. 0 316 796 of DonMichael et al. (published May 24, 1989) discloses an intravascular ultrasonic catheter probe which employs a wire with a bulbous tip at the distal end. The proximal end of the wire is connected with an ultrasonic energy source, and the major part of the wire is confined in a hollow catheter. The distal end of the wire is retracted into the catheter during introduction into a blood vessel, and the bulbous distal end is thereupon expelled from the distal end of the catheter to act upon a stenosis while the energy source is active to vibrate the wire. The distal end of the wire is necessarily small because it must be capable of passing through the catheter. A small distal end is likely to perforate and/or otherwise damage the wall surrounding a body cavity.
German patent application No. 38 02 550 of Borodulin et al. (published Aug. 11, 1988) discloses a vibratory probe within a deformable bulbous distal end of a catheter. The distal end of the probe repeatedly expands the distal end of the catheter radially and axially to thus push a foreign body (such as a stone) through the body cavity. The apparatus of Borodulin can shift mobile foreign bodies in a urinary tract or in another body cavity but is highly unlikely to successfully attack a stenosis or an occlusion in a blood vessel because the radially and axially expandable bulbous distal end of the catheter is actually a balloon which is too soft to be useful in connection with the treatment of stenoses and/or occlusions.
German Pat. No. 34 19 962 to Okada (granted Mar. 1, 1990) discloses a high-frequency incision and excision apparatus which is designed for removal of polyps and operates with a wire loop.
European patent application No. 0 177 782 of Auth (published Apr. 16, 1986) discloses a transluminal thrombectomy apparatus wherein a drive shaft is rotated to withdraw the fibrin of the thrombus and to thus establish a path for the flow of blood. The major part of the shaft is confined in a flexible tubular housing.
German Utility Model No. G 73 26 151.5 of Wolf (published Oct. 4, 1973) discloses an endoscopic coagulation probe wherein a hollow metallic head is inserted into the distal end of a flexible hose and is filled with a heat-resistant material. The heat-resistant material confines an electric heating element for the head, and the conductors connecting such heating element with an energy source extend from the distal end to the proximal end of the hose. The hose can be replaced with a tube.